Infants are easy targets for viruses and bacteria, as their immune responses lack the punch to ward off pathogens. Zhang et al. (page 1107) now find that young immune systems are well developed but are sabotaged by a group of childish B cells.
In adults, microbes trigger defense responses by activating Toll-Like Receptors (TLRs) on dendritic cells (DCs). The DCs then ramp up defense by secreting Interferons α and β (IFN α/β), which are toxic to pathogens, and pro-inflammatory TNF and interleukin-12 (IL-12), which reinforce inflammation by activating T cells.
In newborns, however, TNF and IL-12 are only weakly produced during inflammation, even though neonatal DCs produce these cytokines when stimulated in vitro. To identify the in vivo roadblock, Zhang et al. focused on the anti-inflammatory cytokine IL-10, as it is a known inhibitor of TNF and IL-12 production. In an earlier study, the...
